X-ray diffraction study of a bulk, polycrystalline Ag-9 at. pct Sn alloy deformed in compression

Abstract

An analysis was made of X-ray powder pattern peaks from a bulk, polycrystalline Ag-9at. pct Sn alloy that was plastically deformed by compression. The shapes and positions of all available (hkl) reflections were recorded using the focusing, Bragg-Brentano X-ray geometry. Fourier analysis of the profiles were carried out on (111)–(222), (200)–(400), and (220)–(440) pairs of reflections. The effective particle sizesDe(hkl) decreased rapidly with increasing deformation and reached values ofDe(111)=110A,De(100)=40A, andDe(110)=90A beyond 20 pct reduction in thickness. The anistropy of the particle sizes is interpreted as a consequence of faulting in the deformed alloy. The mean square strains in the [111] direction were of the order of 10−5 after more than 20 pct reduction in thickness. Lattice parameter measurements yield the deformation fault probability (α≈0.02), and the residual stresses. The variation of the true lattice parameterao with increasing deformation indicated that segregation occurred in the deformed alloy. From the ratio of 〈e2〉/α (≈ 6 × 10−4), a nominal stacking fault energy of 6 erg per sq cm was calculated.